Davemk1

38" maybe not. Dave

www.kirkframeworks.com dave

Hey there, The pleasure was all mine with your visit. The ride with Joe was great and hanging and talking for a bit with others that understand the Seven thing was really fun too. You all are welcome anytime. dave

So my Birkin finally got some new kicks (wheels to us old folks). I previously had the stock Birkin wheels which are silly heavy and in my case not so round. So I got these new wheels from Good-Win racing. They sell Miata stuff and had the magic combo of 15 x 7 with a 30mm backspace and at a very reasonable price. With lightweight and round wheels mounted it's uncommonly smooth now. I took this photo this evening as the light was so sweet and had to share. All the best, Dave http://www.usa7s.com/aspnetforum/upload/1529439625_DSC_0141.jpg

It's my very simple and a bit crude front splitter. It's made from 1/8" ABS sheet. There is a vent in the front face of it that leads to a hose that runs back and pushes air into the bottom of the foot box to help keep my feet from getting cooked............ it works pretty well with a nice flow of air. dave

I just recently put new wheels on my Birkin............ it sure is nice having wheels that are actually round. Crazy I know. I'm running 215/45's in the rear and 195/50's up front and they fill the fenders pretty well. I got them from Good-Win Racing and they are Team Dynamics wheels meant for a Miata. They are 15 x 7 with a 30mm backspace. They are fairly light at 12 or so pounds and they are pretty cheap. The center bore to fit the Spec Miata is too small for the Birkin (needs 60.1mm front on my car) so Good-Win had them bored out for me for $10 a wheel and he did a nice job. So there are aren't too many 30mm BS wheels out there but there are a few. Dave http://www.usa7s.com/aspnetforum/upload/906589361_DSC_9996.jpg

I have the T1R on my Birkin for street use. They are very good even in heavy rain and the traction in the dry is fine. Not anything like a R compound tire or a slick by any means but fine for the street. They are pretty quiet and it seems like they will never wear out. I autocross on slicks and just wanted a smooth quiet tire that handled rain well for those long drives home after an event and the inevitable afternoon thunderstorm. Dave

That's good............ with all those guns out there we are bound to be safer and have less risk of gun related violence. or maybe not. dave

FWIW stock Birkin wheels are 15 x 7 with a 30mm offset. dave

I set up mine with Brooklands screens. I bent a piece of 1" x 1/4" aluminum strap and then mounted the motorcycle mirrors and screens to it. Not as cool as a carbon thing but they work very well and my hat even stays on at 70mph! dave http://www.usa7s.com/aspnetforum/upload/601708953_DSC_6465.jpg

One issue you might find on a Birkin (maybe other sevens too) is that the rear track is already almost 3" wider than the front. If you add to this substantially I'll bet you add understeer in a big way as the rear grip will go up a good bit while the front will stay the same. I suppose you could consider doing the fronts too but this is project creep in a big way at the fenders would need to be modified...............not to mention the fact that your scrub radius would be huge and the stress on the front spindles might be scary. In the end it might be easier to put on narrower fenders dave

+1 Let's hope that sometime soon the folks that have risked their lives for our safety get the treatment, healthcare both physical and mental, and respect that they so richly deserve. They deserve all we can give them. dave

I paid $3.97 for 91 octane ( the highest we can get here) in Bozeman yesterday. Dave

I don't notice much in the way of power drop. If............ if there is any it's at the very high end of the RPM range and not a place I spend much time while driving on the street. With the Supertrapp thingie you can vary the amount of backpressure with the number of discs you use. At first I used all of them for the least amount of backpressure. I found it had a bit more bark that I liked so I removed a few and it took the edge off nicely. As I recall I'm running 9 of the 12 discs right now. My system replaces the stock, rear exit Birkin system and either way (with or without tip) it pulls MUCH harder with the new side exit system. I'm sure some of the power gain comes from the shortness of the system. I look forward to seeing how it does on the dyno. I dyno'd the car with the old exhaust and power started to drop off at about 5500 rpms. It felt that way too. It now feels like power builds all the way to cut off. It will be interesting to see if my seat of the pants deal is in line with the dyno. I hope that helps. dave

I use a DNA truck muffler (longest one) on my Birkin. For the street I have a Supertrapp tip that I slip over and clamp on. It keeps the sound to a reasonable level that I personally don't find too loud. Then when I race autocross I take the tip off and let it flow. It's turned out to be a very good way to go for me. dave

Eggsactly...........but remember that if your rear end carries less than 51% of the weight you get to pull off another 35 pounds. Dave

I don't believe that's true. I'd have to double check but I'm pretty sure it's the actual driver. When you are pulled into impound at a divisional or national event they have you (your helmet and all that) get in the car when it's weighed. If it was a flat amount for driver weight they'd just weigh the car and then add that flat amount and come up with a total.................. now as I think of this if the driver weight was "fixed" then you wouldn't have any mention of it in the book. It would just be car weight since driver weight wouldn't matter. Does that make sense? If you go to the SCCA site you can download the rule book and see what it says. dave

A few autocross friends and I bought some scales for corner weighting so it's really simple. Put the car on the scales, put the read-out next to the car where you can see it, plunk your butt in the saddle and see what you've got. In a perfect world the corner weights would be 50% and the right-left balance would also be 50%. But the world isn't perfect so while it's easy to get a 50% corner weight it's near impossible to get a 50% right-left. So I just concentrate on the corner weight. The only way to offset my near 200# of driver and helmet would be to add a lot of weight to the passenger side. I've removed as much weight as possible from the driver side to help but it's a token effort really. So corner weighting - I get the car set up EXACTLY how I race it. Race slicks set up with proper air pressure, 1/4 tank of fuel, my helmet on my head (yes it feels silly sitting in your car standing still in your garage with your helmet on), etc. Look at the read out and make a plan as to what spring to adjust, make the adjustment and recheck. The scales are very sensitive and can tell the difference between my hands on the steering wheel and my hand in my lap. Not that it matters really but why not go all the way. Tweak, check, tweak, and repeat. It's very easy really. My car weighs 1241 (in race trim) without me in it and 1431 with me in the car. I have a 50% corner weight and 49.4% front and 50.6% rear. 53.6% of the weight is on the driver's side and 46.4% on the passenger. As for the car weight and the SCCA. It's a bit convoluted and you need to look closely at the rule book. The min weight for DM (weight with driver) is 1380 with a 2.0L motor. But there are two additional weight considerations. One is that the Birkin ( and most Sevens) incur a 40# modified tub penalty. So the min weight then becomes 1420 for a Birkin. But (there's always a 'but' isn't there?) there is another more obscure rule that says IF you have less than 51% of the weight on the drive wheels you can deduct another 35#. So with my car, since it's weight distribution is less than 51% rear I can consider removing weight from the car AS LONG AS I don't end up with 51% or more of the weight on the rear. In my case this means I can effectively remove weight from the middle to the rear of the car, get the weight down to the adjusted min of 1385. For me this means at large important events I'll remove the windshield (and gain a big aero advantage- 11 pounds) and the rear luggage tray (4.5 pounds) which will bring my weight down to 1415 and still have less than 51% of the weight on the rear. Due to the variable weight of the fuel and the fact that not all scales read the same I want to stay about 20 pounds over the limit just in case. All this said I think the whole weight deal is only important at large events where they actually impound the car and weigh it. If you just want to compete locally and have fun then corner weight the car and don't worry about the overall weight. No one else will care and you will no doubt be above the min unless you try hard to not be. But if you want to compete on a national level it all matters. So far I've done well locally but have never been to the big show in Topeka. I hope to go this year. I'm sure I will get my butt kicked with the HP I'm running (145) but that makes the whole weight deal even more important. Plus the whole thing is interesting and fun for me. I hope that helps. dave

It's dead simple and really cheap. I used black ASB sheet from McMaster Carr. If you haven't heard of them they are the giant of industrial supply online. I used 1/16" sheet and it cost about $10 for enough material for both sides. Making them was simple. The Birkin has aluminum spats that are riveted on. I drilled out the rivets and removed the spats. I then taped them down to the ABS sheet and traced with a sharpie marker. I also drilled the ABS for the rivets by just passing the drill bit through the old and into the new pieces. I then cut the ABS with tin snips ( I think heavy kitchen shears would do it). Now all you need to do is rivet the new ones on and have a good dark beer while sitting alone in the garage. The last part is optional. have fun. Dave

The driveshaft hoops come from Woody at MSI. My era of Birkin had the driveshaft tunnel riveted in so I got to drill out 48 rivets. A fun day. I made the splitter out of 1/8" ABS sheet and angle aluminum. The whole deal just bolts on and weighs less than 3 pounds. I have no idea if it "works" but I doubt it hurts and I was underweight for Dmod anyway. Another way to look at it might be to say it must work as I haven't slid off the road yet! Thanks for asking. dave P.S..........the little grill in the splitter is to keep big bugs out of the fresh air intake I've run from the splitter to the foot box. I hate when bees go up my pants! http://www.usa7s.com/aspnetforum/upload/608352650_DSC_9010.jpghttp://www.usa7s.com/aspnetforum/upload/1146541531_DSC_9046.jpghttp://www.usa7s.com/aspnetforum/upload/1214039026_DSC_9049.jpg

It's been a very cold and snowy spring here in Bozeman but we have had some days to get out on clear roads. The Bridger Mountains are in the background and my home is near the base of the mountains as viewed from this spot. Really good driving round here. I've done a bunch of work on my Birkin in the past month and it's all coming together just in time for our first autocross race this weekend. I've recently - 1) installed an emergency cut off switch 2) installed driveshaft safety hoops (fun drilling rivets!) 3) made and installed a front splitter 4) corner weighted and balanced 5) made a passenger side cone deflector for the rear fender 6) made new ABS fender spats for the rear fenders to replace the ratty alloy versions. The added side benefit is that they are quieter when rocks whack them. Now it's time for a fun summer. Dave http://www.usa7s.com/aspnetforum/upload/1546558906_DSC_9025.jpg

Hagerty for my Birkin. Agreed value and unlimited mileage. They asked how many miles a year I might drive the car and I told them 10,000. They asked where am I going with all those miles. I told them that everything in MT is far away and I work from home and drive for fun. OK they said. I think I pay something like $320 for the year. Dave

I've never seen a drain on my ZX1. I use the lovely "loosen a hose and slide it off slowly and get the fluid all over your shirt sleeve and floor" technique. Is there another way? dave

I'm sorry.........both are sold at this point. dave

I saw that yesterday.......nice looking car. The one thing I wonder about is where the battery is? Normally they are above the passenger footwell. dave